Does Legalising Cannabis Increase Crime? What Studies Found

Legalisation debates produced firm predictions in both directions. Opponents expected rising crime, more youth use and more road deaths. Advocates expected illicit markets to collapse and law enforcement resources to be freed.

Enough time has now passed in early-legalising jurisdictions to check. The results are mostly undramatic, with one area of genuine concern.

Violent and Property Crime

Studies examining crime trends in states that legalised have generally not found consistent increases in violent crime. Some analyses report reductions in certain categories, others find no significant change, and results vary by jurisdiction and method.

Border-region research has been used to argue reductions, on the reasoning that legal supply undercuts trafficking organisations. Findings here are contested and sensitive to specification.

The honest summary is that legalisation did not produce a detectable crime wave, and claims of large crime reductions are not well supported either. The most defensible reading is that the effect on general crime rates is small enough to be hard to measure against everything else moving at the same time.

Arrests Fell, Which Was the Point

The clearest and least surprising effect is a sharp drop in cannabis possession arrests in legalising jurisdictions. That is legalisation working as designed rather than a finding about criminality.

Two important qualifications:

Racial disparities in remaining enforcement have persisted in several jurisdictions. Fewer arrests overall has not consistently meant proportionate arrests, and disparities in cannabis-adjacent charges have continued.

Other offences remain. Public consumption, unlicensed sale, cultivation above limits and underage possession are still enforceable, so cannabis arrests did not go to zero.

Youth Use

This was the loudest prediction, and it has not been borne out.

Long-running surveys of adolescent substance use, including the Monitoring the Future study, have generally shown youth cannabis use rates remaining stable or declining through the legalisation period, rather than rising as feared.

Plausible explanations include licensed retailers checking identification more reliably than illicit sellers, cannabis already being widely available to teenagers beforehand, and general declines in adolescent substance use across categories.

Two caveats. Method of use has shifted, with vaping and edibles more common among young people who do use, and accidental paediatric ingestion has risen substantially, which is a genuine harm distinct from teenage use.

Impaired Driving: The Real Concern

This is where the concern is legitimate and the evidence is messier.

Some studies have reported increases in crash rates and in cannabis involvement in crashes following legalisation, while others find no significant change. The picture is complicated by three genuine problems:

Testing changed. More post-crash cannabis testing after legalisation means more detections, which inflates apparent increases independent of any behaviour change.

Detection is not impairment. THC-COOH or even THC presence indicates use, not that the driver was impaired at the time.

Polysubstance use. Alcohol is frequently involved, and separating contributions is difficult.

What is not in doubt is that cannabis impairs driving. Reaction time, tracking, attention and decision-making are all affected, and combining cannabis with alcohol produces worse impairment than either alone.

The unresolved policy problem is that there is no reliable roadside impairment test equivalent to breath alcohol. Per se blood THC limits are scientifically weak, since blood levels fall steeply while impairment persists and chronic users carry residual THC while unimpaired.

The Illicit Market Did Not Disappear

Advocates expected legal supply to displace illicit sales. It has partially, and unlicensed markets persist at a larger scale than anticipated in several jurisdictions, for economic reasons: high taxes, licence scarcity, local retail bans, and compliance costs that unlicensed sellers avoid.

This matters for the crime question because a persistent illicit market means persistent illicit-market enforcement and the associated harms.

Dispensaries and Local Crime

Research on whether dispensaries increase neighbourhood crime is mixed. Some studies report localised increases, plausibly related to cash-heavy businesses being robbery targets, which is a consequence of banking exclusion rather than of cannabis. Others report no effect or reductions attributed to increased security and foot traffic.

Bottom Line

Legalisation did not produce the predicted crime wave, and evidence for large crime reductions is also weak. Possession arrests fell sharply while racial disparities in remaining enforcement persisted, and youth use rates have stayed stable or declined. Impaired driving is the legitimate concern, complicated by increased testing, the gap between detection and impairment, and the absence of any reliable roadside impairment test.

Disclaimer: This article is for educational purposes only and does not constitute legal advice.